1. Field of the Invention
This invention concerns a container for use in the transportation of perishable foods that can transport perishable foods such as vegetables, fruits or fishes and meats without degrading their freshness.
2. Description of the Prior Art
For maintaining the freshness of perishable foods, it is generally required to preserve the perishable foods at optimal low temperature conditions depending on the type of foods. For instance, in the case of tables and fruits, it is required to store them under low temperature conditions i.e., within a range of temperature that is not so low as to cause low temperature injury. In the case of those fishes and meats, the taste of which will change upon freezing, low temperature conditions within such a range of temperature so as not to cause freezing are required and, further, in the case of those fishes and meats which are freezable, low temperature conditions corresponding thereto are required.
For transporting such perishable foods, containers have been employed that transport perishable foods while keeping them under adequate temperature conditions by circulating cold along the inner wall surfaces of the chamber with an aim of keeping them cool and fresh during transportation.
However, since the perishable foods contained in the storage chamber are merely cooled by the cold air circulated along the inner wall surface of the storage chamber in such conventional transportation containers, if an optimum low temperature condition can be maintained by the sufficient cooling at a region near the inner wall surface, the cooling effect of the cold air is reduced as it travels through the inner wall surface and approaches the central portion of the storage chamber. This results in a temperature slope of several .degree.C. or greater over the range from the vicinity of the inner wall surface to the central region of the storage chamber. Then, the freshness of the perishable foods stored at the central region is reduced, particularly, in the case of vegetables and fruits that dissipate heat during transportation due to aspiration or after-ripening effect. If the power of a cooler, etc. is increased for compensating such reduction in the cooling effect, it will inevitably increase the final cost of the perishable foods, and may chill the food stored near end surfaces of the wall.
In view of the above, the present inventors have already proposed a container for the transportation of perishable foods which comprises, in addition to main recycling cold air flows circulated within the storage chamber, auxiliary recycling cold air flows circulated substantially perpendicular to the direction of the main recycling cold air flows (Japanese Patent Laid-Open Publication No. 177687/1982).
The transportation container proposed by the present inventors can overcome the various problems in the conventional transportation containers as described above and has actually attained certain satisfactory results. However, it requires gaps to be formed through which the auxiliary recycling cold air flows are passed on each of lateral side wall surfaces, in addition to the gaps through which the main recycling cold air flows are passed on each of the upper and lower as well as front and back wall surfaces. This reduces the effective containing capacity of the storage chamber by so much and, further, requires fences and like other equipments to each of the side wall surfaces for preventing the cargoes from breaking loose and gap maintaining means for advancing or retracting the fences, etc. This results in a further additional problem of increased cost in the transportation and of troublesome loading works.